It is known to use a rotary rockwheel assembly pulled by a tractor for cutting a narrow trench in the ground, for example for installation of television cables and other services beneath the surface of a road or pavement. The cutting wheel of such an assembly has a plurality of carbide teeth attached to its outer rim and is driven in a clockwise or anti-clockwise direction by the power take-off from the tractor. Furthermore the cutting wheel is supported by the tractor by way of a pivot linkage permitting the rotating cutting wheel to be lowered into the ground to commence cutting of the trench. The tractor may then be moved forward as rotation of the cutting wheel continues so as to continue cutting of the trench. However, there are certain disadvantages associated with such rockwheel assemblies in use. Because the cutting wheel is directly carried by the pivot linkage shock and vibration are transmitted from the cutting wheel to the linkage and to the tractor, and there is a tendency for the depth of trench to vary uncontrollably. Furthermore when used for cutting through the surface of a tarmac road or pavement such assemblies produce trenches having ragged edges due to the fact that the cutting wheel has a tendency to break away stones at the edges of the trench. This means that, in many applications, it is necessary to subsequently smooth the edges of the trench in a separate operation using an inclined saw. This significantly increases the trench cutting costs.
U.S. Pat. No. 2,403,367 discloses a rotary rockwheel assembly in which the cutting wheel is carried by a support arrangement such that the cutting wheel may be lowered relative to the support arrangement for cutting, and in which a skid is pivotally secured to the support arrangement to track a sufficient distance from the trench being cut so as to avoid breaking in of the edges of the trench. However, because the support arrangement is not supported on the ground by the skid, there is still substantial transmission of shock and vibration from the cutting wheel to the linkage and the tractor.
It is an object of the invention to provide an improved rotary rockwheel assembly which is capable of cutting a trench in a particularly efficient manner.